AccuCover&reg; Rifle Scope & Gun Sight Flip Up Cover Accuracy Aiming Device Reduces Parallax Error E3841 (38-41mm) AccuCover is an entirely new concept in scope cover design. As you'd expect from a manufacturer of quality scope covers, it provides excellent protection of your scope and lens against whatever elements you can throw at it. However, what really makes AccuCover unique is its ingenious patented design which helps you shoot both faster and more accurately. The addition of high visibility markings on the rim of the scope cover come into play when you take aim, your eyes traditionally focus on the crosshairs within the scope and the target behind. With AccuCover, your peripheral vision also comes into play, sensing the four markings on the rim and helping to keep your eye aligned with both the crosshairs and target. Other benefits are faster acquisition of the target, reduction of gun cant and faster eye alignment. Original patented AccuCover shooting enhancement for telescopic rifle scopes. Suitable for scopes with Occular diameter between 35 and 44mm (1 3/8" - 1 3/4") When the high visibility markings, crosshairs and target are all aligned, you get the perfect shot.